A procedure for operating a particulate filter situated in the exhaust gas area of an internal combustion engine is known from German Published Patent Application No. 103 33 441, a lambda signal supplied by a lambda sensor being used as a measure of the particulate burn-off rate. The determined measure is used for monitoring the particulate matter burn-off temperature with the objective of preventing the particulate filter from overheating. A setpoint value is specified for the lambda signal or for a change in the lambda signal. If a discrepancy is detected between the setpoint value and the actual value, an intervention is made, for example, in the position of a throttle valve, the charging pressure of an exhaust-gas turbocharger or the determination of an exhaust gas recirculation rate. An embodiment provides a control element situated at the exhaust gas channel, via which fuel or an oxidant is fed to the exhaust gas flow.
A procedure for minimizing pollutants in exhaust gases of an internal combustion engine, in particular nitrogen oxides, is known from German Patent No. 44 04 681, which provides for an extensive removal of the nitrogen oxide component of the intake air of the internal combustion engine. The ambient air taken in by the internal combustion engine enters an air separation unit which makes air enriched with nitrogen available at one outlet and air enriched with oxygen at another outlet. The oxygen is obtained by an air separation unit containing a membrane which is only permeable to oxygen molecules.
The exhaust gas temperature is increased by the oxygen enrichment of the ambient air taken in by the internal combustion engine. An exhaust gas treatment device situated in the exhaust gas channel of the internal combustion engine, a catalytic converter for example, reaches a required minimum operating temperature more quickly after a cold start. At the same time, the fuel conversion in the internal combustion engine is improved so that the untreated carbon monoxide and hydrocarbon emissions are reduced.
The procedure for reducing pollutants in exhaust gases of an internal combustion engine known from German Published Patent Application No. 197 10 842, nitrogen oxides in particular, also provides for supplying the internal combustion engine with intake air enriched with oxygen. The focus is on the rapid attainment of the minimum operating temperature of a catalytic converter which is achieved using an operating point-dependent admixture of oxygen to the intake air. The air separation unit is situated in a bypass channel of the intake port of the internal combustion engine.
Another possibility for reaching the minimum operating temperature of a catalytic converter as rapidly as possible is described in German Published Patent Application No. 41 41 946 which provides for feeding secondary air into the exhaust gas area of the internal combustion engine as a function of the operating state of the internal combustion engine. The oxygen component of the secondary air may oxidize the oxidizable constituents contained in the exhaust gas such as carbon monoxide, hydrocarbons or hydrogen. The exothermic oxidation reaction may already occur in the exhaust manifold under appropriate conditions. If necessary, the oxidation reaction takes place in an oxidation catalytic converter. The exhaust gas which is additionally heated after the combustion process in the internal combustion engine indirectly heats an exhaust gas treatment device situated in the exhaust gas area, a catalytic converter or a particulate filter, for example, via the increased exhaust gas temperature. If necessary, it may be provided for the exhaust gas treatment device to contain a catalytic coating so that the oxidation reaction occurs directly in the exhaust gas treatment device to be heated.
The procedure known from German Published Patent Application No. 197 10 841 provides for a reduction of exhaust gas pollutants using a catalytic converter which is based on such a feed of secondary air into the exhaust gas area of an internal combustion engine. The secondary air is enriched by oxygen supplied by an air separation unit which contains a ceramic membrane permeable to oxygen molecules.